Here's an idea! Let's get reeaaaal pedantic about what it means for an object to be truly "immovable" (i.e. "un-accelerateable") and a force to actually be unstoppable (spoiler: all forces are unstoppable) and use the thought experiment to answer one of the oldest, most ancient questions to ever come up ever. Turns out Minute Physics' Henry Reich is just the man for the job.